[libav.git] / doc / general.texi
1 \input texinfo @c -*- texinfo -*-
3 @settitle General Documentation
4 @titlepage
5 @sp 7
6 @center @titlefont{General Documentation}
7 @sp 3
8 @end titlepage
11 @chapter external libraries
13 FFmpeg can be hooked up with a number of external libraries to add support
14 for more formats. None of them are used by default, their use has to be
15 explicitly requested by passing the appropriate flags to @file{./configure}.
17 @section AMR
19 AMR comes in two different flavors, WB and NB. FFmpeg can make use of the
20 AMR WB (floating-point mode) and the AMR NB (floating-point mode) reference
21 decoders and encoders.
23 Go to @url{http://www.penguin.cz/~utx/amr} and follow the instructions for
24 installing the libraries. Then pass @code{--enable-libamr-nb} and/or
25 @code{--enable-libamr-wb} to configure to enable the libraries.
28 @chapter Supported File Formats and Codecs
30 You can use the @code{-formats} option to have an exhaustive list.
32 @section File Formats
34 FFmpeg supports the following file formats through the @code{libavformat}
35 library:
37 @multitable @columnfractions .4 .1 .1 .4
38 @item Supported File Format @tab Encoding @tab Decoding @tab Comments
39 @item MPEG audio @tab X @tab X
40 @item MPEG-1 systems @tab X @tab X
41 @tab muxed audio and video
42 @item MPEG-2 PS @tab X @tab X
43 @tab also known as @code{VOB} file
44 @item MPEG-2 TS @tab @tab X
45 @tab also known as DVB Transport Stream
46 @item ASF@tab X @tab X
47 @item AVI@tab X @tab X
48 @item WAV@tab X @tab X
49 @item Macromedia Flash@tab X @tab X
50 @tab Only embedded audio is decoded.
51 @item FLV @tab X @tab X
52 @tab Macromedia Flash video files
53 @item Real Audio and Video @tab X @tab X
54 @item Raw AC3 @tab X @tab X
55 @item Raw MJPEG @tab X @tab X
56 @item Raw MPEG video @tab X @tab X
57 @item Raw PCM8/16 bits, mulaw/Alaw@tab X @tab X
58 @item Raw CRI ADX audio @tab X @tab X
59 @item Raw Shorten audio @tab @tab X
60 @item SUN AU format @tab X @tab X
61 @item NUT @tab X @tab X @tab NUT Open Container Format
62 @item QuickTime @tab X @tab X
63 @item MPEG-4 @tab X @tab X
64 @tab MPEG-4 is a variant of QuickTime.
65 @item Raw MPEG4 video @tab X @tab X
66 @item DV @tab X @tab X
67 @item 4xm @tab @tab X
68 @tab 4X Technologies format, used in some games.
69 @item Playstation STR @tab @tab X
70 @item Id RoQ @tab X @tab X
71 @tab Used in Quake III, Jedi Knight 2, other computer games.
72 @item Interplay MVE @tab @tab X
73 @tab Format used in various Interplay computer games.
74 @item WC3 Movie @tab @tab X
75 @tab Multimedia format used in Origin's Wing Commander III computer game.
76 @item Sega FILM/CPK @tab @tab X
77 @tab Used in many Sega Saturn console games.
78 @item Westwood Studios VQA/AUD @tab @tab X
79 @tab Multimedia formats used in Westwood Studios games.
80 @item Id Cinematic (.cin) @tab @tab X
81 @tab Used in Quake II.
82 @item FLIC format @tab @tab X
83 @tab .fli/.flc files
84 @item Sierra VMD @tab @tab X
85 @tab Used in Sierra CD-ROM games.
86 @item Sierra Online @tab @tab X
87 @tab .sol files used in Sierra Online games.
88 @item Matroska @tab X @tab X
89 @item Electronic Arts Multimedia @tab @tab X
90 @tab Used in various EA games; files have extensions like WVE and UV2.
91 @item Nullsoft Video (NSV) format @tab @tab X
92 @item ADTS AAC audio @tab X @tab X
93 @item Creative VOC @tab X @tab X @tab Created for the Sound Blaster Pro.
94 @item American Laser Games MM @tab @tab X
95 @tab Multimedia format used in games like Mad Dog McCree
96 @item AVS @tab @tab X
97 @tab Multimedia format used by the Creature Shock game.
98 @item Smacker @tab @tab X
99 @tab Multimedia format used by many games.
100 @item GXF @tab X @tab X
101 @tab General eXchange Format SMPTE 360M, used by Thomson Grass Valley playout servers.
102 @item CIN @tab @tab X
103 @tab Multimedia format used by Delphine Software games.
104 @item MXF @tab @tab X
105 @tab Material eXchange Format SMPTE 377M, used by D-Cinema, broadcast industry.
106 @item SEQ @tab @tab X
107 @tab Tiertex .seq files used in the DOS CDROM version of the game Flashback.
108 @item DXA @tab @tab X
109 @tab This format is used in non-Windows version of Feeble Files game and
110 different game cutscenes repacked for use with ScummVM.
111 @item THP @tab @tab X
112 @tab Used on the Nintendo GameCube.
113 @item C93 @tab @tab X
114 @tab Used in the game Cyberia from Interplay.
115 @item Bethsoft VID @tab @tab X
116 @tab Used in some games from Bethesda Softworks.
117 @item CRYO APC @tab @tab X
118 @tab Audio format used in some games by CRYO Interactive Entertainment.
119 @end multitable
121 @code{X} means that encoding (resp. decoding) is supported.
123 @section Image Formats
125 FFmpeg can read and write images for each frame of a video sequence. The
126 following image formats are supported:
128 @multitable @columnfractions .4 .1 .1 .4
129 @item Supported Image Format @tab Encoding @tab Decoding @tab Comments
130 @item PGM, PPM @tab X @tab X
131 @item PAM @tab X @tab X @tab PAM is a PNM extension with alpha support.
132 @item PGMYUV @tab X @tab X @tab PGM with U and V components in YUV 4:2:0
133 @item JPEG @tab X @tab X @tab Progressive JPEG is not supported.
134 @item .Y.U.V @tab X @tab X @tab one raw file per component
135 @item animated GIF @tab X @tab X @tab Only uncompressed GIFs are generated.
136 @item PNG @tab X @tab X @tab 2 bit and 4 bit/pixel not supported yet.
137 @item Targa @tab @tab X @tab Targa (.TGA) image format.
138 @item TIFF @tab X @tab X @tab YUV, JPEG and some extension is not supported yet.
139 @item SGI @tab X @tab X @tab SGI RGB image format
140 @item PTX @tab @tab X @tab V.Flash PTX format
141 @end multitable
143 @code{X} means that encoding (resp. decoding) is supported.
145 @section Video Codecs
147 @multitable @columnfractions .4 .1 .1 .4
148 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
149 @item MPEG-1 video @tab X @tab X
150 @item MPEG-2 video @tab X @tab X
151 @item MPEG-4 @tab X @tab X
152 @item MSMPEG4 V1 @tab X @tab X
153 @item MSMPEG4 V2 @tab X @tab X
154 @item MSMPEG4 V3 @tab X @tab X
155 @item WMV7 @tab X @tab X
156 @item WMV8 @tab X @tab X @tab not completely working
157 @item WMV9 @tab @tab X @tab not completely working
158 @item VC1 @tab @tab X
159 @item H.261 @tab X @tab X
160 @item H.263(+) @tab X @tab X @tab also known as RealVideo 1.0
161 @item H.264 @tab @tab X
162 @item RealVideo 1.0 @tab X @tab X
163 @item RealVideo 2.0 @tab X @tab X
164 @item MJPEG @tab X @tab X
165 @item lossless MJPEG @tab X @tab X
166 @item JPEG-LS @tab X @tab X @tab fourcc: MJLS, lossless and near-lossless is supported
167 @item Apple MJPEG-B @tab @tab X
168 @item Sunplus MJPEG @tab @tab X @tab fourcc: SP5X
169 @item DV @tab X @tab X
170 @item HuffYUV @tab X @tab X
171 @item FFmpeg Video 1 @tab X @tab X @tab experimental lossless codec (fourcc: FFV1)
172 @item FFmpeg Snow @tab X @tab X @tab experimental wavelet codec (fourcc: SNOW)
173 @item Asus v1 @tab X @tab X @tab fourcc: ASV1
174 @item Asus v2 @tab X @tab X @tab fourcc: ASV2
175 @item Creative YUV @tab @tab X @tab fourcc: CYUV
176 @item Sorenson Video 1 @tab X @tab X @tab fourcc: SVQ1
177 @item Sorenson Video 3 @tab @tab X @tab fourcc: SVQ3
178 @item On2 VP3 @tab @tab X @tab still experimental
179 @item On2 VP5 @tab @tab X @tab fourcc: VP50
180 @item On2 VP6 @tab @tab X @tab fourcc: VP60,VP61,VP62
181 @item Theora @tab X @tab X @tab still experimental
182 @item Intel Indeo 3 @tab @tab X
183 @item FLV @tab X @tab X @tab Sorenson H.263 used in Flash
184 @item Flash Screen Video @tab X @tab X @tab fourcc: FSV1
185 @item ATI VCR1 @tab @tab X @tab fourcc: VCR1
186 @item ATI VCR2 @tab @tab X @tab fourcc: VCR2
187 @item Cirrus Logic AccuPak @tab @tab X @tab fourcc: CLJR
188 @item 4X Video @tab @tab X @tab Used in certain computer games.
189 @item Sony Playstation MDEC @tab @tab X
190 @item Id RoQ @tab X @tab X @tab Used in Quake III, Jedi Knight 2, other computer games.
191 @item Xan/WC3 @tab @tab X @tab Used in Wing Commander III .MVE files.
192 @item Interplay Video @tab @tab X @tab Used in Interplay .MVE files.
193 @item Apple Animation @tab X @tab X @tab fourcc: 'rle '
194 @item Apple Graphics @tab @tab X @tab fourcc: 'smc '
195 @item Apple Video @tab @tab X @tab fourcc: rpza
196 @item Apple QuickDraw @tab @tab X @tab fourcc: qdrw
197 @item Cinepak @tab @tab X
198 @item Microsoft RLE @tab @tab X
199 @item Microsoft Video-1 @tab @tab X
200 @item Westwood VQA @tab @tab X
201 @item Id Cinematic Video @tab @tab X @tab Used in Quake II.
202 @item Planar RGB @tab @tab X @tab fourcc: 8BPS
203 @item FLIC video @tab @tab X
204 @item Duck TrueMotion v1 @tab @tab X @tab fourcc: DUCK
205 @item Duck TrueMotion v2 @tab @tab X @tab fourcc: TM20
206 @item VMD Video @tab @tab X @tab Used in Sierra VMD files.
207 @item MSZH @tab @tab X @tab Part of LCL
208 @item ZLIB @tab X @tab X @tab Part of LCL, encoder experimental
209 @item TechSmith Camtasia @tab @tab X @tab fourcc: TSCC
210 @item IBM Ultimotion @tab @tab X @tab fourcc: ULTI
211 @item Miro VideoXL @tab @tab X @tab fourcc: VIXL
212 @item QPEG @tab @tab X @tab fourccs: QPEG, Q1.0, Q1.1
213 @item LOCO @tab @tab X @tab
214 @item Winnov WNV1 @tab @tab X @tab
215 @item Autodesk Animator Studio Codec @tab @tab X @tab fourcc: AASC
216 @item Fraps FPS1 @tab @tab X @tab
217 @item CamStudio @tab @tab X @tab fourcc: CSCD
218 @item American Laser Games Video @tab @tab X @tab Used in games like Mad Dog McCree
219 @item ZMBV @tab X @tab X @tab Encoder works only on PAL8
220 @item AVS Video @tab @tab X @tab Video encoding used by the Creature Shock game.
221 @item Smacker Video @tab @tab X @tab Video encoding used in Smacker.
222 @item RTjpeg @tab @tab X @tab Video encoding used in NuppelVideo files.
223 @item KMVC @tab @tab X @tab Codec used in Worms games.
224 @item VMware Video @tab @tab X @tab Codec used in videos captured by VMware.
225 @item Cin Video @tab @tab X @tab Codec used in Delphine Software games.
226 @item Tiertex Seq Video @tab @tab X @tab Codec used in DOS CDROM FlashBack game.
227 @item DXA Video @tab @tab X @tab Codec originally used in Feeble Files game.
228 @item AVID DNxHD @tab @tab X @tab aka SMPTE VC3
229 @item C93 Video @tab @tab X @tab Codec used in Cyberia game.
230 @item THP @tab @tab X @tab Used on the Nintendo GameCube.
231 @item Bethsoft VID @tab @tab X @tab Used in some games from Bethesda Softworks.
232 @item Renderware TXD @tab @tab X @tab Texture dictionaries used by the Renderware Engine.
233 @end multitable
235 @code{X} means that encoding (resp. decoding) is supported.
237 @section Audio Codecs
239 @multitable @columnfractions .4 .1 .1 .1 .7
240 @item Supported Codec @tab Encoding @tab Decoding @tab Comments
241 @item MPEG audio layer 2 @tab IX @tab IX
242 @item MPEG audio layer 1/3 @tab IX @tab IX
243 @tab MP3 encoding is supported through the external library LAME.
244 @item AC3 @tab IX @tab IX
245 @tab liba52 is used internally for decoding.
246 @item Vorbis @tab X @tab X
247 @item WMA V1/V2 @tab X @tab X
248 @item AAC @tab X @tab X
249 @tab Supported through the external library libfaac/libfaad.
250 @item Microsoft ADPCM @tab X @tab X
251 @item MS IMA ADPCM @tab X @tab X
252 @item QT IMA ADPCM @tab @tab X
253 @item 4X IMA ADPCM @tab @tab X
254 @item G.726 ADPCM @tab X @tab X
255 @item Duck DK3 IMA ADPCM @tab @tab X
256 @tab Used in some Sega Saturn console games.
257 @item Duck DK4 IMA ADPCM @tab @tab X
258 @tab Used in some Sega Saturn console games.
259 @item Westwood Studios IMA ADPCM @tab @tab X
260 @tab Used in Westwood Studios games like Command and Conquer.
261 @item SMJPEG IMA ADPCM @tab @tab X
262 @tab Used in certain Loki game ports.
263 @item CD-ROM XA ADPCM @tab @tab X
264 @item CRI ADX ADPCM @tab X @tab X
265 @tab Used in Sega Dreamcast games.
266 @item Electronic Arts ADPCM @tab @tab X
267 @tab Used in various EA titles.
268 @item Creative ADPCM @tab @tab X
269 @tab 16 -> 4, 8 -> 4, 8 -> 3, 8 -> 2
270 @item THP ADPCM @tab @tab X
271 @tab Used on the Nintendo GameCube.
272 @item RA144 @tab @tab X
273 @tab Real 14400 bit/s codec
274 @item RA288 @tab @tab X
275 @tab Real 28800 bit/s codec
276 @item RADnet @tab X @tab IX
277 @tab Real low bitrate AC3 codec, liba52 is used for decoding.
278 @item AMR-NB @tab X @tab X
279 @tab Supported through an external library.
280 @item AMR-WB @tab X @tab X
281 @tab Supported through an external library.
282 @item DV audio @tab @tab X
283 @item Id RoQ DPCM @tab X @tab X
284 @tab Used in Quake III, Jedi Knight 2, other computer games.
285 @item Interplay MVE DPCM @tab @tab X
286 @tab Used in various Interplay computer games.
287 @item Xan DPCM @tab @tab X
288 @tab Used in Origin's Wing Commander IV AVI files.
289 @item Sierra Online DPCM @tab @tab X
290 @tab Used in Sierra Online game audio files.
291 @item Apple MACE 3 @tab @tab X
292 @item Apple MACE 6 @tab @tab X
293 @item FLAC lossless audio @tab X @tab X
294 @item Shorten lossless audio @tab @tab X
295 @item Apple lossless audio @tab @tab X
296 @tab QuickTime fourcc 'alac'
297 @item FFmpeg Sonic @tab X @tab X
298 @tab experimental lossy/lossless codec
299 @item Qdesign QDM2 @tab @tab X
300 @tab there are still some distortions
301 @item Real COOK @tab @tab X
302 @tab All versions except 5.1 are supported
303 @item DSP Group TrueSpeech @tab @tab X
304 @item True Audio (TTA) @tab @tab X
305 @item Smacker Audio @tab @tab X
306 @item WavPack Audio @tab @tab X
307 @item Cin Audio @tab @tab X
308 @tab Codec used in Delphine Software games.
309 @item Intel Music Coder @tab @tab X
310 @item Musepack @tab @tab X
311 @tab Only SV7 is supported
312 @item DT$ Coherent Audio @tab @tab X
313 @item ATRAC 3 @tab @tab X
314 @end multitable
316 @code{X} means that encoding (resp. decoding) is supported.
318 @code{I} means that an integer-only version is available, too (ensures high
319 performance on systems without hardware floating point support).
321 @chapter Platform Specific information
323 @section BSD
325 BSD make will not build FFmpeg, you need to install and use GNU Make
326 (@file{gmake}).
328 @section Windows
330 To get help and instructions for using FFmpeg under Windows, check out
331 the FFmpeg Windows Help Forum at
332 @url{http://arrozcru.no-ip.org/ffmpeg/}.
334 @subsection Native Windows compilation
336 @itemize
337 @item Install the current versions of MSYS and MinGW from
338 @url{http://www.mingw.org/}. You can find detailed installation
339 instructions in the download section and the FAQ.
341 NOTE: Use at least bash 3.1. Older versions are known to be failing on the
342 configure script.
344 @item If you want to test the FFplay, also download
345 the MinGW development library of SDL 1.2.x
346 (@file{SDL-devel-1.2.x-mingw32.tar.gz}) from
347 @url{http://www.libsdl.org}. Unpack it in a temporary directory, and
348 unpack the archive @file{i386-mingw32msvc.tar.gz} in the MinGW tool
349 directory. Edit the @file{sdl-config} script so that it gives the
350 correct SDL directory when invoked.
352 @item If you want to use vhooks, you must have a POSIX compliant libdl in your
353 MinGW system. Get dlfcn-win32 from @url{http://code.google.com/p/dlfcn-win32}.
355 @item Extract the current version of FFmpeg.
357 @item Start the MSYS shell (file @file{msys.bat}).
359 @item Change to the FFmpeg directory and follow
360 the instructions of how to compile FFmpeg (file
361 @file{INSTALL}). Usually, launching @file{./configure} and @file{make}
362 suffices. If you have problems using SDL, verify that
363 @file{sdl-config} can be launched from the MSYS command line.
365 @item You can install FFmpeg in @file{Program Files/FFmpeg} by typing
366 @file{make install}. Do not forget to copy @file{SDL.dll} to the place
367 you launch @file{ffplay} from.
369 @end itemize
371 Notes:
372 @itemize
374 @item The target @file{make wininstaller} can be used to create a
375 Nullsoft based Windows installer for FFmpeg and FFplay. @file{SDL.dll}
376 must be copied to the FFmpeg directory in order to build the
377 installer.
379 @item By using @code{./configure --enable-shared} when configuring FFmpeg,
380 you can build @file{avcodec.dll} and @file{avformat.dll}. With
381 @code{make install} you install the FFmpeg DLLs and the associated
382 headers in @file{Program Files/FFmpeg}.
384 @item Visual C++ compatibility: If you used @code{./configure --enable-shared}
385 when configuring FFmpeg, FFmpeg tries to use the Microsoft Visual
386 C++ @code{lib} tool to build @code{avcodec.lib} and
387 @code{avformat.lib}. With these libraries you can link your Visual C++
388 code directly with the FFmpeg DLLs (see below).
390 @end itemize
392 @subsection Visual C++ compatibility
394 FFmpeg will not compile under Visual C++ -- and it has too many
395 dependencies on the GCC compiler to make a port viable. However,
396 if you want to use the FFmpeg libraries in your own applications,
397 you can still compile those applications using Visual C++. An
398 important restriction to this is that you have to use the
399 dynamically linked versions of the FFmpeg libraries (i.e. the
400 DLLs), and you have to make sure that Visual-C++-compatible
401 import libraries are created during the FFmpeg build process.
403 This description of how to use the FFmpeg libraries with Visual C++ is
404 based on Visual C++ 2005 Express Edition Beta 2. If you have a different
405 version, you might have to modify the procedures slightly.
407 Here are the step-by-step instructions for building the FFmpeg libraries
408 so they can be used with Visual C++:
410 @enumerate
412 @item Install Visual C++ (if you have not done so already).
414 @item Install MinGW and MSYS as described above.
416 @item Add a call to @file{vcvars32.bat} (which sets up the environment
417 variables for the Visual C++ tools) as the first line of
418 @file{msys.bat}. The standard location for @file{vcvars32.bat} is
419 @file{C:\Program Files\Microsoft Visual Studio 8\VC\bin\vcvars32.bat},
420 and the standard location for @file{msys.bat} is
421 @file{C:\msys\1.0\msys.bat}. If this corresponds to your setup, add the
422 following line as the first line of @file{msys.bat}:
424 @code{call "C:\Program Files\Microsoft Visual Studio 8\VC\bin\vcvars32.bat"}
426 @item Start the MSYS shell (file @file{msys.bat}) and type @code{link.exe}.
427 If you get a help message with the command line options of @code{link.exe},
428 this means your environment variables are set up correctly, the
429 Microsoft linker is on the path and will be used by FFmpeg to
430 create Visual-C++-compatible import libraries.
432 @item Extract the current version of FFmpeg and change to the FFmpeg directory.
434 @item Type the command
435 @code{./configure --enable-shared --disable-static --enable-memalign-hack}
436 to configure and, if that did not produce any errors,
437 type @code{make} to build FFmpeg.
439 @item The subdirectories @file{libavformat}, @file{libavcodec}, and
440 @file{libavutil} should now contain the files @file{avformat.dll},
441 @file{avformat.lib}, @file{avcodec.dll}, @file{avcodec.lib},
442 @file{avutil.dll}, and @file{avutil.lib}, respectively. Copy the three
443 DLLs to your System32 directory (typically @file{C:\Windows\System32}).
445 @end enumerate
447 And here is how to use these libraries with Visual C++:
449 @enumerate
451 @item Create a new console application ("File / New / Project") and then
452 select "Win32 Console Application". On the appropriate page of the
453 Application Wizard, uncheck the "Precompiled headers" option.
455 @item Write the source code for your application, or, for testing, just
456 copy the code from an existing sample application into the source file
457 that Visual C++ has already created for you. (Note that your source
458 filehas to have a @code{.cpp} extension; otherwise, Visual C++ will not
459 compile the FFmpeg headers correctly because in C mode, it does not
460 recognize the @code{inline} keyword.) For example, you can copy
461 @file{output_example.c} from the FFmpeg distribution (but you will
462 have to make minor modifications so the code will compile under
463 C++, see below).
465 @item Open the "Project / Properties" dialog box. In the "Configuration"
466 combo box, select "All Configurations" so that the changes you make will
467 affect both debug and release builds. In the tree view on the left hand
468 side, select "C/C++ / General", then edit the "Additional Include
469 Directories" setting to contain the complete paths to the
470 @file{libavformat}, @file{libavcodec}, and @file{libavutil}
471 subdirectories of your FFmpeg directory. Note that the directories have
472 to be separated using semicolons. Now select "Linker / General" from the
473 tree view and edit the "Additional Library Directories" setting to
474 contain the same three directories.
476 @item Still in the "Project / Properties" dialog box, select "Linker / Input"
477 from the tree view, then add the files @file{avformat.lib},
478 @file{avcodec.lib}, and @file{avutil.lib} to the end of the "Additional
479 Dependencies". Note that the names of the libraries have to be separated
480 using spaces.
482 @item Now, select "C/C++ / Code Generation" from the tree view. Select
483 "Debug" in the "Configuration" combo box. Make sure that "Runtime
484 Library" is set to "Multi-threaded Debug DLL". Then, select "Release" in
485 the "Configuration" combo box and make sure that "Runtime Library" is
486 set to "Multi-threaded DLL".
488 @item Click "OK" to close the "Project / Properties" dialog box and build
489 the application. Hopefully, it should compile and run cleanly. If you
490 used @file{output_example.c} as your sample application, you will get a
491 few compiler errors, but they are easy to fix. The first type of error
492 occurs because Visual C++ does not allow an @code{int} to be converted to
493 an @code{enum} without a cast. To solve the problem, insert the required
494 casts (this error occurs once for a @code{CodecID} and once for a
495 @code{CodecType}). The second type of error occurs because C++ requires
496 the return value of @code{malloc} to be cast to the exact type of the
497 pointer it is being assigned to. Visual C++ will complain that, for
498 example, @code{(void *)} is being assigned to @code{(uint8_t *)} without
499 an explicit cast. So insert an explicit cast in these places to silence
500 the compiler. The third type of error occurs because the @code{snprintf}
501 library function is called @code{_snprintf} under Visual C++. So just
502 add an underscore to fix the problem. With these changes,
503 @file{output_example.c} should compile under Visual C++, and the
504 resulting executable should produce valid video files.
506 @end enumerate
508 @subsection Cross compilation for Windows with Linux
510 You must use the MinGW cross compilation tools available at
511 @url{http://www.mingw.org/}.
513 Then configure FFmpeg with the following options:
514 @example
515 ./configure --target-os=mingw32 --cross-prefix=i386-mingw32msvc-
516 @end example
517 (you can change the cross-prefix according to the prefix chosen for the
518 MinGW tools).
520 Then you can easily test FFmpeg with Wine
521 (@url{http://www.winehq.com/}).
523 @subsection Compilation under Cygwin
525 Cygwin works very much like Unix.
527 Just install your Cygwin with all the "Base" packages, plus the
528 following "Devel" ones:
529 @example
530 binutils, gcc-core, make, subversion
531 @end example
533 Do not install binutils-20060709-1 (they are buggy on shared builds);
534 use binutils-20050610-1 instead.
536 Then run
538 @example
539 ./configure --enable-static --disable-shared
540 @end example
542 to make a static build or
544 @example
545 ./configure --enable-shared --disable-static
546 @end example
548 to build shared libraries.
550 If you want to build FFmpeg with additional libraries, download Cygwin
551 "Devel" packages for Ogg and Vorbis from any Cygwin packages repository
552 and/or SDL, xvid, faac, faad2 packages from Cygwin Ports,
553 (@url{http://cygwinports.dotsrc.org/}).
555 @subsection Crosscompilation for Windows under Cygwin
557 With Cygwin you can create Windows binaries that do not need the cygwin1.dll.
559 Just install your Cygwin as explained before, plus these additional
560 "Devel" packages:
561 @example
562 gcc-mingw-core, mingw-runtime, mingw-zlib
563 @end example
565 and add some special flags to your configure invocation.
567 For a static build run
568 @example
569 ./configure --target-os=mingw32 --enable-memalign-hack --enable-static --disable-shared --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
570 @end example
572 and for a build with shared libraries
573 @example
574 ./configure --target-os=mingw32 --enable-memalign-hack --enable-shared --disable-static --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
575 @end example
577 @section BeOS
579 BeOS support is broken in mysterious ways.
581 @chapter Developers Guide
583 @section API
584 @itemize @bullet
585 @item libavcodec is the library containing the codecs (both encoding and
586 decoding). Look at @file{libavcodec/apiexample.c} to see how to use it.
588 @item libavformat is the library containing the file format handling (mux and
589 demux code for several formats). Look at @file{ffplay.c} to use it in a
590 player. See @file{output_example.c} to use it to generate audio or video
591 streams.
593 @end itemize
595 @section Integrating libavcodec or libavformat in your program
597 You can integrate all the source code of the libraries to link them
598 statically to avoid any version problem. All you need is to provide a
599 'config.mak' and a 'config.h' in the parent directory. See the defines
600 generated by ./configure to understand what is needed.
602 You can use libavcodec or libavformat in your commercial program, but
603 @emph{any patch you make must be published}. The best way to proceed is
604 to send your patches to the FFmpeg mailing list.
606 @node Coding Rules
607 @section Coding Rules
609 FFmpeg is programmed in the ISO C90 language with a few additional
610 features from ISO C99, namely:
611 @itemize @bullet
612 @item
613 the @samp{inline} keyword;
614 @item
615 @samp{//} comments;
616 @item
617 designated struct initializers (@samp{struct s x = @{ .i = 17 @};})
618 @item
619 compound literals (@samp{x = (struct s) @{ 17, 23 @};})
620 @end itemize
622 These features are supported by all compilers we care about, so we will not
623 accept patches to remove their use unless they absolutely do not impair
624 clarity and performance.
626 All code must compile with GCC 2.95 and GCC 3.3. Currently, FFmpeg also
627 compiles with several other compilers, such as the Compaq ccc compiler
628 or Sun Studio 9, and we would like to keep it that way unless it would
629 be exceedingly involved. To ensure compatibility, please do not use any
630 additional C99 features or GCC extensions. Especially watch out for:
631 @itemize @bullet
632 @item
633 mixing statements and declarations;
634 @item
635 @samp{long long} (use @samp{int64_t} instead);
636 @item
637 @samp{__attribute__} not protected by @samp{#ifdef __GNUC__} or similar;
638 @item
639 GCC statement expressions (@samp{(x = (@{ int y = 4; y; @})}).
640 @end itemize
642 Indent size is 4.
643 The presentation is the one specified by 'indent -i4 -kr -nut'.
644 The TAB character is forbidden outside of Makefiles as is any
645 form of trailing whitespace. Commits containing either will be
646 rejected by the Subversion repository.
648 The main priority in FFmpeg is simplicity and small code size in order to
649 minimize the bug count.
651 Comments: Use the JavaDoc/Doxygen
652 format (see examples below) so that code documentation
653 can be generated automatically. All nontrivial functions should have a comment
654 above them explaining what the function does, even if it is just one sentence.
655 All structures and their member variables should be documented, too.
656 @example
657 /**
658 * @@file mpeg.c
659 * MPEG codec.
660 * @@author ...
661 */
663 /**
664 * Summary sentence.
665 * more text ...
666 * ...
667 */
668 typedef struct Foobar@{
669 int var1; /**< var1 description */
670 int var2; ///< var2 description
671 /** var3 description */
672 int var3;
673 @} Foobar;
675 /**
676 * Summary sentence.
677 * more text ...
678 * ...
679 * @@param my_parameter description of my_parameter
680 * @@return return value description
681 */
682 int myfunc(int my_parameter)
683 ...
684 @end example
686 fprintf and printf are forbidden in libavformat and libavcodec,
687 please use av_log() instead.
689 Casts should be used only when necessary. Unneeded parentheses
690 should also be avoided if they don't make the code easier to understand.
692 @section Development Policy
694 @enumerate
695 @item
696 Contributions should be licensed under the LGPL 2.1, including an
697 "or any later version" clause, or the MIT license. GPL 2 including
698 an "or any later version" clause is also acceptable, but LGPL is
699 preferred.
700 @item
701 You must not commit code which breaks FFmpeg! (Meaning unfinished but
702 enabled code which breaks compilation or compiles but does not work or
703 breaks the regression tests)
704 You can commit unfinished stuff (for testing etc), but it must be disabled
705 (#ifdef etc) by default so it does not interfere with other developers'
706 work.
707 @item
708 You do not have to over-test things. If it works for you, and you think it
709 should work for others, then commit. If your code has problems
710 (portability, triggers compiler bugs, unusual environment etc) they will be
711 reported and eventually fixed.
712 @item
713 Do not commit unrelated changes together, split them into self-contained
714 pieces. Also do not forget that if part B depends on part A, but A does not
715 depend on B, then A can and should be committed first and separate from B.
716 Keeping changes well split into self-contained parts makes reviewing and
717 understanding them on the commit log mailing list easier. This also helps
718 in case of debugging later on.
719 Also if you have doubts about splitting or not splitting, do not hesitate to
720 ask/discuss it on the developer mailing list.
721 @item
722 Do not change behavior of the program (renaming options etc) without
723 first discussing it on the ffmpeg-devel mailing list. Do not remove
724 functionality from the code. Just improve!
726 Note: Redundant code can be removed.
727 @item
728 Do not commit changes to the build system (Makefiles, configure script)
729 which change behavior, defaults etc, without asking first. The same
730 applies to compiler warning fixes, trivial looking fixes and to code
731 maintained by other developers. We usually have a reason for doing things
732 the way we do. Send your changes as patches to the ffmpeg-devel mailing
733 list, and if the code maintainers say OK, you may commit. This does not
734 apply to files you wrote and/or maintain.
735 @item
736 We refuse source indentation and other cosmetic changes if they are mixed
737 with functional changes, such commits will be rejected and removed. Every
738 developer has his own indentation style, you should not change it. Of course
739 if you (re)write something, you can use your own style, even though we would
740 prefer if the indentation throughout FFmpeg was consistent (Many projects
741 force a given indentation style - we do not.). If you really need to make
742 indentation changes (try to avoid this), separate them strictly from real
743 changes.
745 NOTE: If you had to put if()@{ .. @} over a large (> 5 lines) chunk of code,
746 then either do NOT change the indentation of the inner part within (do not
747 move it to the right)! or do so in a separate commit
748 @item
749 Always fill out the commit log message. Describe in a few lines what you
750 changed and why. You can refer to mailing list postings if you fix a
751 particular bug. Comments such as "fixed!" or "Changed it." are unacceptable.
752 @item
753 If you apply a patch by someone else, include the name and email address in
754 the log message. Since the ffmpeg-cvslog mailing list is publicly
755 archived you should add some SPAM protection to the email address. Send an
756 answer to ffmpeg-devel (or wherever you got the patch from) saying that
757 you applied the patch.
758 @item
759 When applying patches that have been discussed (at length) on the mailing
760 list, reference the thread in the log message.
761 @item
762 Do NOT commit to code actively maintained by others without permission.
763 Send a patch to ffmpeg-devel instead. If no one answers within a reasonable
764 timeframe (12h for build failures and security fixes, 3 days small changes,
765 1 week for big patches) then commit your patch if you think it is OK.
766 Also note, the maintainer can simply ask for more time to review!
767 @item
768 Subscribe to the ffmpeg-cvslog mailing list. The diffs of all commits
769 are sent there and reviewed by all the other developers. Bugs and possible
770 improvements or general questions regarding commits are discussed there. We
771 expect you to react if problems with your code are uncovered.
772 @item
773 Update the documentation if you change behavior or add features. If you are
774 unsure how best to do this, send a patch to ffmpeg-devel, the documentation
775 maintainer(s) will review and commit your stuff.
776 @item
777 Try to keep important discussions and requests (also) on the public
778 developer mailing list, so that all developers can benefit from them.
779 @item
780 Never write to unallocated memory, never write over the end of arrays,
781 always check values read from some untrusted source before using them
782 as array index or other risky things.
783 @item
784 Remember to check if you need to bump versions for the specific libav
785 parts (libavutil, libavcodec, libavformat) you are changing. You need
786 to change the version integer and the version string.
787 Incrementing the first component means no backward compatibility to
788 previous versions (e.g. removal of a function from the public API).
789 Incrementing the second component means backward compatible change
790 (e.g. addition of a function to the public API).
791 Incrementing the third component means a noteworthy binary compatible
792 change (e.g. encoder bug fix that matters for the decoder).
793 @item
794 If you add a new codec, remember to update the changelog, add it to
795 the supported codecs table in the documentation and bump the second
796 component of the @file{libavcodec} version number appropriately. If
797 it has a fourcc, add it to @file{libavformat/avienc.c}, even if it
798 is only a decoder.
799 @item
800 Do not change code to hide warnings without ensuring that the underlying
801 logic is correct and thus the warning was inappropriate.
802 @item
803 If you add a new file, give it a proper license header. Do not copy and
804 paste it from a random place, use an existing file as template.
805 @end enumerate
807 We think our rules are not too hard. If you have comments, contact us.
809 Note, these rules are mostly borrowed from the MPlayer project.
811 @section Submitting patches
813 First, (@pxref{Coding Rules}) above if you did not yet.
815 When you submit your patch, try to send a unified diff (diff '-up'
816 option). We cannot read other diffs :-)
818 Also please do not submit a patch which contains several unrelated changes.
819 Split it into separate, self-contained pieces. This does not mean splitting
820 file by file. Instead, make the patch as small as possible while still
821 keeping it as a logical unit that contains an individual change, even
822 if it spans multiple files. This makes reviewing your patches much easier
823 for us and greatly increases your chances of getting your patch applied.
825 Run the regression tests before submitting a patch so that you can
826 verify that there are no big problems.
828 Patches should be posted as base64 encoded attachments (or any other
829 encoding which ensures that the patch will not be trashed during
830 transmission) to the ffmpeg-devel mailing list, see
831 @url{http://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel}
833 It also helps quite a bit if you tell us what the patch does (for example
834 'replaces lrint by lrintf'), and why (for example '*BSD isn't C99 compliant
835 and has no lrint()')
837 Also please if you send several patches, send each patch as a separate mail,
838 do not attach several unrelated patches to the same mail.
840 @section patch submission checklist
842 @enumerate
843 @item
844 Do the regression tests pass with the patch applied?
845 @item
846 Is the patch a unified diff?
847 @item
848 Is the patch against latest FFmpeg SVN?
849 @item
850 Are you subscribed to ffmpeg-dev?
851 (the list is subscribers only due to spam)
852 @item
853 Have you checked that the changes are minimal, so that the same cannot be
854 achieved with a smaller patch and/or simpler final code?
855 @item
856 If the change is to speed critical code, did you benchmark it?
857 @item
858 If you did any benchmarks, did you provide them in the mail?
859 @item
860 Have you checked that the patch does not introduce buffer overflows or
861 other security issues?
862 @item
863 Is the patch created from the root of the source tree, so it can be
864 applied with @code{patch -p0}?
865 @item
866 Does the patch not mix functional and cosmetic changes?
867 @item
868 Did you add tabs or trailing whitespace to the code? Both are forbidden.
869 @item
870 Is the patch attached to the email you send?
871 @item
872 Is the mime type of the patch correct? It should be text/x-diff or
873 text/x-patch or at least text/plain and not application/octet-stream.
874 @item
875 If the patch fixes a bug, did you provide a verbose analysis of the bug?
876 @item
877 If the patch fixes a bug, did you provide enough information, including
878 a sample, so the bug can be reproduced and the fix can be verified?
879 Note please do not attach samples >100k to mails but rather provide a
880 URL, you can upload to ftp://upload.mplayerhq.hu
881 @item
882 Did you provide a verbose summary about what the patch does change?
883 @item
884 Did you provide a verbose explanation why it changes things like it does?
885 @item
886 Did you provide a verbose summary of the user visible advantages and
887 disadvantages if the patch is applied?
888 @item
889 Did you provide an example so we can verify the new feature added by the
890 patch easily?
891 @item
892 If you added a new file, did you insert a license header? It should be
893 taken from FFmpeg, not randomly copied and pasted from somewhere else.
894 @item
895 You should maintain alphabetical order in alphabetically ordered lists as
896 long as doing so does not break API/ABI compatibility.
897 @item
898 Lines with similar content should be aligned vertically when doing so
899 improves readability.
900 @item
901 Did you provide a suggestion for a clear commit log message?
902 @end enumerate
904 @section Patch review process
906 All patches posted to ffmpeg-devel will be reviewed, unless they contain a
907 clear note that the patch is not for SVN.
908 Reviews and comments will be posted as replies to the patch on the
909 mailing list. The patch submitter then has to take care of every comment,
910 that can be by resubmitting a changed patch or by discussion. Resubmitted
911 patches will themselves be reviewed like any other patch. If at some point
912 a patch passes review with no comments then it is approved, that can for
913 simple and small patches happen immediately while large patches will generally
914 have to be changed and reviewed many times before they are approved.
915 After a patch is approved it will be committed to the repository.
917 We will review all submitted patches, but sometimes we are quite busy so
918 especially for large patches this can take several weeks.
920 When resubmitting patches, please do not make any significant changes
921 not related to the comments received during review. Such patches will
922 be rejected. Instead, submit significant changes or new features as
923 separate patches.
925 @section Regression tests
927 Before submitting a patch (or committing to the repository), you should at least
928 test that you did not break anything.
930 The regression tests build a synthetic video stream and a synthetic
931 audio stream. These are then encoded and decoded with all codecs or
932 formats. The CRC (or MD5) of each generated file is recorded in a
933 result file. A 'diff' is launched to compare the reference results and
934 the result file.
936 The regression tests then go on to test the FFserver code with a
937 limited set of streams. It is important that this step runs correctly
938 as well.
940 Run 'make test' to test all the codecs and formats.
942 Run 'make fulltest' to test all the codecs, formats and FFserver.
944 [Of course, some patches may change the results of the regression tests. In
945 this case, the reference results of the regression tests shall be modified
946 accordingly].
948 @bye